Snubber Circuit Resonance for Transistor Ringing Suppression
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Solution Overview
Problem
Existing electric power conversion devices face challenges in suppressing ringing phenomena, which are voltage/current vibrations occurring after transistor switching, despite advancements in surge voltage suppression techniques.
Innovation Solution
The proposed electric power conversion device incorporates a snubber circuit with a snubber capacitor, inductor element, and resistor connected in series, parallel with a smoothing capacitor, where the resonance frequency of the snubber circuit is aligned with the ringing frequency of the transistor, and the impedance of the snubber circuit loop is made lower than that of the smoothing capacitor loop at resonance, allowing current components to flow through the snubber circuit and be dissipated by the resistor, effectively converging ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transistor switching speed is improved, then power conversion efficiency is enhanced, but surge voltage and ringing increase
Solution Approach 1:
The snubber circuit acts as an intermediary element between the transistor and the rest of the circuit. It provides a controlled path for the high-frequency ringing currents generated by fast switching, allowing these currents to circulate through the resonant LC circuit and be dissipated by the resistor rather than propagating through the main power circuit. This mediator approach enables fast switching while suppressing the harmful effects of resulting ringing.
2Object-affected harmful factors
If a snubber circuit is added to suppress ringing, then ringing is suppressed, but device complexity increases
Solution Approach 1:
The patent merges the snubber circuit components (capacitor, inductor, resistor) into a unified resonant circuit configuration that is connected in parallel with the existing smoothing capacitor. This integrated approach allows the snubber circuit to function as a cohesive unit that suppresses ringing through resonance, rather than requiring separate independent suppression circuits for different frequency components, thereby limiting the increase in complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables quick suppression of ringing by ensuring that current vibration components flow through the snubber circuit, where they are attenuated by the resistor, thereby reducing noise and improving the stability of the power conversion process.
Implementation Method 1
The capacitance of the snubber capacitor, the inductance of the inductor element and the magnitude of the resistor are set such that a resonance frequency of the snubber circuit coincides with a ringing frequency of the transistor
Implementation Method 2
energy is consumed by the resistor. That is, it is possible to quickly converge ringing
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
If the capacitance of a snubber capacitor (22), the inductance of a coil (23) and the magnitude of a resistor (21) are specified such that the resonance frequency of the snubber circuit (20) coincides with the ringing frequency of the transistor (16), and the impedance of the first loop at the resonance frequency becomes smaller than the impedance of the second loop at the resonance frequency, a current component due to ringing flows in the snubber circuit (20), and energy is consumed by the resistor (21). Therefore, it is possible to quickly converge ringing.